Gravity carburetor feed

ABSTRACT

An auxiliary fuel supply device including an auxiliary tank connected remotely or directly to a vehicle carburetor for supplying and maintaining fuel within the carburetor. The auxiliary tank has a discharge line connected to the carburetor and an inlet line connected to the fuel pump, the inlet line opening into the auxiliary tank at an elevation substantially above the elevation of the discharge opening to the carburetor. The opening of the inlet line into the tank is at an elevation above the float valve of the carburetor to permit fuel to flow by gravity from the auxiliary tank to the carburetor to compensate for fuel losses within the carburetor, such as by vaporization. The auxiliary fuel tank contains a vent system having a one-way check valve for permitting air at substantially atmospheric pressure to enter the tank to effectively permit fuel to flow from the tank to the carburetor as needed when the vehicle engine and the fuel pump are inoperative.

United States Patent [72] lnventor Robert E. Mott 405 Parkwood Ave., Kalamazoo, Mich. 49001 [21] Appl. No. 806,443 [22] Filed Mar. 12, 1969 [45] Patented Aug. 10, 1971 [54] GRAVITY CARBURETOR FEED 2 Claims, 4 Figs.

[52] US. Cl 137/389, 137/575, 137/583 (51] Int. Cl F16k 15/04 [50] Field ofSeareh 137/386,

[56] References Cited UNITED STATES PATENTS 1,492,474 4/1924 Lewis 137/587 1,564,061 12/1925 Hale 137/587 X 2,103,516 12/1937 Dempsey. 137/587 X 2,274,532 2/1942 Dach 261/73 X 2,672,189 3/1954 Welch 137/587 X 3,048,958 8/1962 Barnes 3,123,249 3/1964 Gorandetal.

ABSTRACT: An auxiliary fuel supply device including an auxiliary tank connected remotely or directly to a vehicle carburetor for supplying and maintaining fuel within the carburetor. The auxiliary tank has a discharge line connected to the carburetor and an inlet line connected to the fuel pump, the inlet line opening into the auxiliary tank at an elevation substantially above the elevation of the discharge opening to the carburetor. The opening of the inlet line into the tank is at an elevation above the float valve of the carburetor to permit fuel to flow by gravity from the auxiliary tank to the carburetor to compensate for fuel losses within the carburetor, such as by vaporization. The auxiliary fuel tank contains a vent system having a one-way check valve for permitting air at substantially atmospheric pressure to enter the tank to effectively permit fuel to flow from the tank to the carburetor as needed when the vehicle engine and the fuel pump are inoperative.

PATENTED mm 0 l97l 1%. 5598 l4 3 sum 2 OF 2 IN VENTOR. P055 5 M077 GRAVITY CARBURETOR FEED FIELD OF THE INVENTION This invention relates to a fuel supply system for the engine of a vehicle, such as an automobile, and particularly relates to an improved auxiliary fuel supply tank connected between the carburetor and the fuel pump for maintaining a predetermined amount of fuel within the carburetor to facilitate starting of the engine.

BACKGROUND OF THE INVENTION In most automobiles, the carburetor is positioned adjacent to the upper portion of the engine directly beneath the air cleaner such that the air cleaner at least partially surrounds the carburetor. Further, the fuel pump is generally positioned at an elevation below the carburetor with the fuel supply line from the fuel pump to the carburetor generally entering the carburetor at or adjacent the bottom side thereof. The carburetor, as is well known, contains a float valve which automatically functions to maintain a predetermined level or quantity of fuel within the carburetor, the float valve automatically opening when the fuel level within the carburetor drops below this predetermined level to permit more fuel to be supplied from the fuel pump to the carburetor. This arrangement of the fuel pump and carburetor works satisfactory under driving conditions or when the vehicle is not allowed to stand for long periods of time. However, this fuel system often results in hard starting of the engine, particularly when the vehicle has been allowed to stand for extended periods of time, or when the vehicle has been driven at highway speeds for substantial periods of time and is then permitted to stand for several hours.

For example, when a vehicle has been driven at highway speeds, such as 70 m.p.h., for several hours and is then permitted to stand for several hours, such as overnight, a later attempt to start the engine often results in hard starting of the engine since the carburetor is substantially empty of fuel. Thus, the engine must be cranked by the battery for a substantial time in order for the fuel pump to again operate to supply sufficient fuel to the carburetor to permit starting of the engine. Such long cranking periods ambient not only annoying to the driver of the vehicle, but also are unduly damaging to the vehicle battery, wiring, ignition points, and starter.

It has been determined that the above hard-starting condition is caused by a boiloff of the fuel contained within the carburetor after the engine is stopped. Particularly, after a vehicle has been driven at high speeds for a substantial period of time, the engine is at an elevated temperature. Thus, when the engine is stopped, the engine emits a substantial amount of heat as same cools back to the normal ambient temperature. Further, most of this heat rises upwardly around the carburetor and, since the carburetor is substantially surrounded by the air cleaner, an appreciable amount of heat is trapped by the air cleaner, whereupon the carburetor is maintained at an elevated temperature for a substantial time period after the engine is shut off. This trapped heat causes some of the fuel within the carburetor to boil off or vaporize, which loss of fuel then causes the carburetor float valve to open. However, since the fuel pump is inoperative, and further since the fuel pump and the main fuel tank are positioned at an elevation below the fuel supply inlet to the carburetor, the opening of the float valve permits the remaining fuel within the carburetor and the fuel in the line connecting the fuel pump to the carburetor to drain back to the fuel tank. This drain back of fuel thus results in the carburetor being substantially emptied of fuel whereupon a subsequent attempt to start the vehicle is made unduly difficult due to the lack of fuel within the carburetor.

A similar drain back also often occurs when a vehicle has been permitted to stand for a substantial period of time, such as for a week or more, without being started. The carburetor, as is well known, is in communication with the atmosphere and thus the fuel within the carburetor continuously undergoes a small amount of evaporation when the vehicle is standing. Thus, when the engine is permitted to stand inactive for an extended period of time, sufficient evaporation often occurs to cause the float valve to open, whereupon the remaining fuel within the carburetor drains back to the fuel tank, thereby substantially emptying the carburetor and resulting in a hard starting of the engine when a later attempt is made to start same.

The phenomenon of fuel drain back also creates a further problem which is often referred to as vapor lock. Conventional fuel pumps normally operate efficiently only when the pump is filled with fuel. However, when the fuel pump is empty of fuel, and the engine is being cranked during starting, the fuel pump must draw fuel from the main tank through the interconnecting supply line. This transfer of fuel from the main tank occurs slowly and thus the engine often has to be cranked for a substantial time period before the fuel reaches the fuel pump, whereupon considerable delay and inconvenience in engine starting occurs.

Accordingly, it is an object of this invention:

1. To provide an improved fuel system for continuously maintaining fuel in the carburetor of a vehicle engine.

2. To provide a system, as aforesaid, which prevents drain back of fuel from the carburetor to eliminate hard engine starting.

3. To provide a system, as aforesaid, which includes an auxiliary supply tank positioned between the carburetor and the fuel pump for supplying fuel, by gravity, to the carburetor.

4. To provide a system, as aforesaid, wherein the auxiliary tank has a chamber therein containing a supply of fuel, the chamber being supplied with fuel from the fuel pump by a fuel-supply line, the auxiliary tank also having a discharge line connecting the tank to the carburetor, the supply line having a discharge opening in the tank at an elevation substantially above the elevation of the inlet opening to the discharge line.

5. To provide a system, as aforesaid, wherein the discharge opening of the fuel-supply line into the auxiliary tank is at an elevation above the float valve of the carburetor to prevent reverse flow of fuel from the carburetor back to the fuel pump.

6. To provide a system, as aforesaid, wherein the auxiliary tank provides for flow of fuel by means of gravity from the auxiliary tank to the carburetor whenever the float valve of the carburetor is open and the engine is stopped.

7. To provide a system, as aforesaid, wherein the auxiliary tank includes a vent having a one-way check valve therein for permitting air to enter the auxiliary tank to permit flow of fuel by means of gravity from the tank to the carburetor.

8. To provide a system, as aforesaid, wherein the vent is connected either to a vacuum source, such as the intake manifold, or to the air cleaner to permit any overflow of fuel to be safely disposed.

9. To provide a system, as aforesaid, which continually maintains a predetermined quantity of fuel in the carburetor and thus insures rapid engine starting even after the engine has been stopped for extended periods of time.

10. To provide a system, as aforesaid, wherein the auxiliary tank assists the fuel pump in supplying fuel to the carburetor during engine starting.

l 1. To provide a system, as aforesaid, wherein the auxiliary tank supplies fuel to the carburetor to facilitate easy starting of the engine, even when the engine fuel pump is initially dry, to thereby overcome the problem ofvapor lock" 12. To provide a system, as aforesaid, wherein the auxiliary tank permits rapid starting of the engine, which in turn permits the fuel pump to rapidly withdraw fuel from the main tank, even when the fuel pump is initially dry or empty offuel.

l3. To provide a system, as aforesaid, which can be easily and economically manufactured and installed on a vehicle engine.

Other objects and purposes of this invention will be apparent to persons acquainted with devices of this type upon reading the following specification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an improved fuel-supply system for a vehicle engine according to the present invention.

FIG. 2 is a cross-sectional elevational view of an auxiliary fuel-supply device constructed according to the present invention for insertion between the fuel pump and the carburetor.

FIG. 3 is a modification of the auxiliary fuel-supply device illustrated in FIG. 2.

FIG. 4 is a further modification of the auxiliary-fuel supply device illustrated in FIG. 2.

Certain terminology will be used in the following description for convenience in reference only and will not be limiting. The words rightwardly and leftwardly will designate the directions in the drawings to which reference is made. The

words upwardly and downwardly will refer to directions in the drawings and will refer to the direction of fuel flow when the fuel system of the present invention is installed on a vehicle engine. The words forwardly" will refer to the normal direction of fuel flow from the fuel pump to the carburetor, whereas rearwardly" will refer to the opposite direction of flow. The words inwardly" and outwardly will refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof and words of similar import.

SUMMARY OF THE INVENTION The objects and purposes of the present invention are met by providing an auxiliary fuel-supply device connected between the carburetor and the fuel pump of a vehicle engine. The auxiliary fuel-supply device comprises a small tank connected to the fuel pump and supplied with fuel by means ofa fuel-supply tube having a discharge opening communicating with the interior of the tank. The auxiliary tank is also connected to the carburetor by means of a discharge tube which has an inlet opening communicating with the interior of the auxiliary tank. The discharge opening of the fuel-supply tube is located at an elevation substantially above the inlet opening of the discharge tube to maintain a predetermined quantity of fuel within the auxiliary tank. The discharge opening of the supply tube is also positioned at an elevation above the carburetor float valve to prevent fuel from draining back from the carburetor when the fuel pump is inoperative. The auxiliary fuel tank further has a vent system communicating with the upper portion of the chamber therein, which vent system contains a one-way check valve for permitting air to flow into the chamber to prevent creation of a vacuum therein, whereby the air is maintained at substantially atmospheric pressure level within the auxiliary tank to permit fuel within the auxiliary tank to flow by means of gravity from the tank to the carburetor whenever the float valve of the carburetor opens and the engine is stopped. Such gravity flow of fuel to the carburetor thus maintains a supply of fuel in the carburetor at all times to facilitate engine starting.

DETAILED DESCRIPTION FIG. 1 schematically illustrates therein a fuel supply system for an engine of a vehicle, particularly an automobile. The fuel supply system according to the present invention is provided with an auxiliary fuel-supply device 11 connected to the float valve chamber of the carburetor 12 by means ofa fuel line 13. The auxiliary fuel-supply device 11 is supplied with fuel from a positive displacement fuel pump 16 by means of a fuel line 17. The fuel pump 16 withdraws fuel from the main fuel tank 18 and does so through an intermediate fuel line 19.

Considering now in detail the auxiliary fuel device 11 as illustrated in FIG. 2, same comprises a cylindrical auxiliary tank 21 having a sidewall 22 interconnected by top and bottom walls 23 and 24. The cylindrical tank is thus substantially closed and defines a closed chamber 26 therein.

The tank 21 is provided with a first opening 27 through the sidewall thereof adjacent the bottom wall 24, whereupon the end of the fuel discharge line 13 extends therethrough so as to communicate with the interior of the chamber 26. The fuel discharge line 13 is fixedly secured in any convenient manner, as by welding or brazing, to the sidewall 22. The end of the tubular fuel pipe 13 is provided with an inlet opening 28 for permitting communication between the chamber 26 and the interior of the fuel line 13.

The sidewall 22 is provided with a further opening 29 therethrough for permitting the end of the fuel-supply pipe 17 to extend therethrough. The fuel-supply pipe 17 is also fixedly secured to the sidewall 22, in any convenient manner, as by welding or brazing. The end of the fuel supply pipe 17 is provided with a discharge opening 31 located within chamber 26 to permit fluid communication from the tubular fuel-supply pipe 17 to the chamber 26.

As illustrated in FIG. 2, the inlet opening 28 of the discharge pipe 13 is generally positioned adjacent the bottom wall 24, whereas the discharge opening 31 of the supply pipe 17 is generally positioned at a substantial elevation above the inlet opening 28, said difference in elevation being designated by the letter H in FIG. 2. This difference in elevation between the openings 28 and 31 results in the lower portion 32 of the chamber 26 being filled with fuel. On the other hand, the portion 33 of the chamber 26 positioned above the discharge opening 31 is generally free of liquid fuel and is normally occupied by air or other suitable gaseous material.

The discharge opening 31 of the supply line 17, as illustrated in FIG. 1, is also positioned at an elevation above the carburetor float chamber valve. Similarly, the inlet opening 28 of the fuel discharge line 13 is also preferably positioned at an elevation above or at least equal to the elevation of the carburetor float chamber valve. The exact purpose for these elevational relationships will be explained hereinafter.

The auxiliary fuel-supply tank 21 (FIG. 2) is also provided with vent means 36 on the upper end thereof to provide communication with the upper chamber portion 33. The vent means includes a cylindrical sleeve 37 which extends through the top wall 23 into the interior of the chamber 26, the sleeve 37 being provided with an external flange 38 thereon which is fixedly secured to the top wall 23 by any suitable means, as by welding. The sleeve 37 is hollow and defines a small intermediate chamber 39 therein. The upper end of the chamber 39 is closed by means of a threaded screw 41 which is threadably engaged with the interior of the sleeve 37. A resilient seal ring 42 is positioned between the head of a screw 41 and the flange 38.

The vent means 36 includes therein a one-way check valve for permitting flow of air into the upper chamber portion 33. The flow of air into the chamber portion 33 is provided by means of a vent tube 43 which has its inner end fixedly secured to the sleeve 37 and positioned within the chamber 39. The vent tube 43 is provided with a vent opening 46 on the end thereof, which opening is surrounded by a valve seat formed on the free end of the tube 43. A valve member 47, preferably in the form of a ball, is normally maintained in engagement with the valve seat formed on the end of the tube 43 so as to effectively close the vent opening 46. The sleeve 37 is further provided with passages 48 which extend radially outwardly through the wall of the sleeve 37 to provide for communication between the intermediate chamber 39 and the upper portion 33 of the chamber 26. The other end of the vent tube 43 may be, in the simplest form of the invention, freely open to the surrounding atmosphere OPERATION The operation of the system embodying the invention will be described in detail hereinbelow for a better understanding thereof.

When an engine having a fuel system according to the present invention is operating, the positive-displacement fuel pump 16 will withdraw fuel from the primary fuel tank 18 through the line 19, whereupon the fuel-pump 16 will force the fuel through the line 17 into the auxiliary tank 11. The fuel in the supply line 17 will be discharged through the opening 31 into the chamber 26 so as to substantially fill the bottom chamber portion 32. The fuel will then flow through the inlet opening 28 into the discharge line 13, whereupon the fuel will be supplied to the float chamber of the carburetor 12 so as to maintain a predetermined quantity of fuel therein for supplying same to the engine in a normal manner. The upper portion 33 of the chamber 26 will generally be filled with a gaseous product, such as air, which will be at substantially atmospheric pressure or compressed to a pressure level slightly above atmospheric pressure due to the pressurized fuel being supplied through the supply pipe 17 into the chamber 26. The air within the upper chamber portion 33 will pass through the passages 48 into the intermediate chamber 39, which air will act on the ball valve 47 and maintain same in engagement with the seat formed on the end of the vent tube 43 so as to effectively close same. During continued operation of the engine, a substantial quantity of fuel will be present in the lower chamber portion 32 at all times, the fluid level within the chamber 26 generally being at least equal to the level of the discharge opening 31. Further, the level of the fluid within the chamber 26 is always at an elevation substantially above the elevation of the carburetor float valve.

Assuming now that the vehicle has been running for an extended period of time at high speed, with the vehicle then being stopped and permitted to stand for a substantial time. The stopped engine will emit substantial quantities of heat which will cause at least a portion of the fuel trapped within the carburetor to evaporate or boil off. This loss of fuel within the carburetor will cause the float valve to open which, in prior known vehicle fuel systems, would permit all of the fuel within the carburetor to drain back to the main fuel tank since the inoperative fuel pump and the main tank are at a lower elevation. However, in the present invention, when the float valve opens due to boiloff or evaporation, a portion of the fuel contained within the lower portion 32 of the chamber 26 tends to flow by means of gravity from the chamber 26 through the discharge line 13 into the float chamber so as to replenish the supply of fuel within the carburetor. Such gravity flow of fuel occurs since the fuel level within the chamber 26, as determined by the opening 31, is at an elevation substantially above the carburetor float chamber.

Since withdrawal of fuel from chamber 26 causes a decrease in the quantity of fuel within the lower portion 32 thereof, which in turn causes an increase in the volume of the upper portion 33, withdrawal of fuel reduces the pressure within the upper chamber 33 and thereby tends to create a partial vacuum therein. This reduction in pressure in the upper portion 33 causes the one-way check valve 47 to open whereupon air flows from the atmosphere through the vent tube 43 into the upper portion 33 so as to maintain the chamber 26 at a substantially constant pressure level, normally atmospheric. Maintenance of constant pressure within the upper chamber portion 33 thus permits the desired quantity of fuel to be freely transferred by means of gravity from the chamber 26 to the float carburetor chamber. The withdrawal of fuel from the chamber 26 causes the fluid level within the chamber 26 to drop to an elevation below the opening 31, whereupon an air gap exists in the fuel line between the carburetor and the fuel pump, which air gap thus positively prevents any drain back of fuel from the auxiliary tank 21 to the fuel pump 16. The auxiliary tank 21 thus maintains a desired predetermined quantity of fuel in the carburetor at all times to result in quick and easy starting of the engine.

After the fuel level in the auxiliary tank 21 has dropped below the opening 31, and when the engine is again started, the carburetor and the auxiliary tank will possess sufficient fuel therein to enable the engine to be started, whereupon the fuel pump 16 will then again supply fuel to the chamber 26, which fuel will force any trapped air within the chamber 26 to pass through the carburetor so that the chamber 26 will again be filled to a level substantially equal to the elevation of the discharge opening 31.

While the system as described above could be continuously vented to the atmosphere by means of the vent tube 43 if desired, it has been found preferable to provide the one-way check valve 47 since otherwise the vent tube creates a potentially hazardous condition. Specifically, by utilizing the normally closed check valve 47, the upper portion 33 of the chamber is maintained in a normally closed condition and thus fuel vapors are prevented from escaping from the tank 21, thereby minimizing fuel losses. Also, the ball 47, by being normally closed, will prevent fuel from accidentally escaping through the vent tube 43, which escaping fuel might accidentally be deposited on the hot engine and thus create a potential fire hazard. However, since it is known that ball valves often do not properly seat, the vent tube 43 may be connected to a suitable fuel disposal zone, such as the intake manifold, whereupon any fuel which might accidentally pass through the vent tube 43 would be deposited into the intake manifold whereupon same could thus be safely burned and disposed of without creating a fire hazard. Connecting the vent tube 43 to the vacuum manifold also creates a suction within the tube 43 which assists in maintaining the ball valve 47 in tight sealing engagement with its seat during normal engine operating conditions.

A further alternative connection for the external end of the vent tube 43 is the engine air cleaner. By connecting the external end of the vent tube 43 to the air cleaner, any fuel which accidentally passes through the vent tube is easily disposed of within the air cleaner so as to not create a fire hazard.

MODIFICATION FIG. 3 illustrates therein a modification of the auxiliary fuelsupply device illustrated in FIG. 2. Specifically, FIG. 3 discloses therein an auxiliary fuel-supply device 11A which is substantially identical to the device of FIG. 2 except that the supply and discharge lines 17A and 13A, respectively, are integrally interconnected as a single tube by means of an intermediate tubular portion 51. Such a structure thus permits the auxiliary supply device to be easily and economically installed on a vehicle and permits economical connection of the fuel tubes to the auxiliary tank since only a single continuous fuel tube is utilized. However, since the fuel must communicate with the chamber 26 formed within the tank 21, the supply portion 17A of the tube is provided with a drilled opening 31A through the sidewall thereof so as to constitute a discharge opening, whereas the discharge portion 13A of the pipe is also provided with an inlet opening 28A drilled through the sidewall thereof, the openings 28A and 31A communicating with the chamber 26 and being further displaced by an elevation H for the same purpose as explained above.

FIG. 4 illustrates therein a further modification 118 which is substantially identical to the device illustrated in FIG. 2 except that the tank is made in two parts to permit easy assembly and disassembly thereof. Specifically, the tank 218 illustrated in FIG. 4 is formed by means ofupper and lower half-shells 53 and 54 which can be suitably formed from a single piece of material, as by being formed, pressed or molded from a plastic material, die cast or other suitable material.

The half-shells 53 and 54 are threadably interconnected by means of a thread formed on the upper free edge 57 of the lower half-shell 54, which thread is engaged by means of a threaded flange 56 formed on the lower free edge of the upper half-shell 53. The threaded flange 56 overlaps the edge of the lower half-shell when the two half-shells are threadably connected to form the closed tank 218. Such a construction of the tank is desirable since it permits the tank to be easily fabricated and assembled, while also permitting the tank to be easily disassembled for cleaning purposes. This construction of the tank 21B is also desirable since it permits a fuel filter 58 to be positioned within the auxiliary tank if desired, which fuel filter can take the place of or be in addition to the fuel filter normally disposed in or near the carburetor. The two-piece tank 21B is easily disassembled to permit the fuel filter 58 to be cleaned or replaced.

The operation of the devices 11A and 118 as illustrated in FIGS. 3 and 4, respectively, are identical to the operation of the device illustrated in FIGS 1 and 2 as explained above.

The embodiments of the invention in which I claim an exclusive property or privilege are defined as follows:

1. An improved fuel system for a vehicle engine, said fuel system comprising in combination a carburetor having a float chamber means therein with a float valve being disposed with said float chamber means, a positive-displacement fuel pump, a main fuel tank, first fuel conduit means connecting said main tank to said fuel pump, and second fuel conduit means connecting said fuel pump to the float chamber means of said carburetor, and an auxiliary fuel supply device including an auxiliary tank connected in series with said second fuel conduit means between the ends thereof so that said auxiliary tank is connected in series with and between said fuel pump and said float chamber means, the improvement wherein said auxiliary fuel supply device includes:

an auxiliary fuel-supply chamber defined within the interior of said auxiliary tank; said second conduit means including a supply conduit extending between and interconnecting said fuel pump and said auxiliary tank and a discharge conduit extending between and interconnecting the auxiliary tank to the float chamber means of the carburetor; said supply conduit having a discharge opening formed therein in communication with said chamber for permitting supply of fuel to said chamber from said fuel P p said discharge conduit having an inlet opening formed therein in communication with said chamber for permitting fuel to be supplied from said chamber to said carburetor;

the discharge opening in said supply conduit being positioned at an elevation substantially above the elevation of (l) the inlet opening formed in said discharge conduit and (2) the carburetor float valve when same is in a closed position; said auxiliary tank and said supply and discharge conduits comprising the only connection between said fuel pump and the carburetor whereby all fuel supplied to the carburetor from the fuel pump must pass through said auxiliary tank; and vent means providing for communication with the interior of the upper portion of said chamber, said vent means including a vent passageway having an opening at one end thereof in communication with the interior of said auxiliary tank adjacent the upper portion of said chamber, said passageway having an opening at the other end thereof located at a point externally of said auxiliary tank; and

said vent means further including a normally closed oneway check valve in sealing engagement with said vent passageway for normally preventing flow from said chamber through said vent passageway, said check valve permitting flow into the upper portion of said chamber whenever the pressure at said external point is greater than the pressure in the upper portion of said chamber to facilitate flow of fuel by means of gravity from said auxiliary tank through said discharge conduit to said carburetor whenever the float valve moves to the open position and the fuel pump is inoperative.

2. Adevice according to claim 1, wherein said vent means includes a vent conduit providing communication between the interior of said auxiliary tank and a point located externally of said tank, the inner end of said conduit being positioned within the interior of said tank and having a valve seat formed thereon, said check valve including a movable ball valve member positionable in sealing engagement with said seat for preventing flow from the interior of said auxiliary tank to a point located externally thereof. 

1. An improved fuel system for a vehicle engine, said fuel system comprising in combination a carburetor having a float chamber means therein with a float valve being disposed with said float chamber means, a positive-displacement fuel pump, a main fuel tank, first fuel conduit means connecting said main tank to said fuel pump, and second fuel conduit means connecting said fuel pump to the float chamber means of said carburetor, and an auxiliary fuel supply device including an auxiliary tank connected in series with said second fuel conduit means between the ends thereof so that said auxiliary tank is connected in series with and between said fuel pump and said float chamber means, the improvement wherein said auxiliary fuel supply device includes: an auxiliary fuel-supply chamber defined within the interior of said auxiliary tank; said second conduit means including a supply conduit extending betweEn and interconnecting said fuel pump and said auxiliary tank and a discharge conduit extending between and interconnecting the auxiliary tank to the float chamber means of the carburetor; said supply conduit having a discharge opening formed therein in communication with said chamber for permitting supply of fuel to said chamber from said fuel pump; said discharge conduit having an inlet opening formed therein in communication with said chamber for permitting fuel to be supplied from said chamber to said carburetor; the discharge opening in said supply conduit being positioned at an elevation substantially above the elevation of (1) the inlet opening formed in said discharge conduit and (2) the carburetor float valve when same is in a closed position; said auxiliary tank and said supply and discharge conduits comprising the only connection between said fuel pump and the carburetor whereby all fuel supplied to the carburetor from the fuel pump must pass through said auxiliary tank; and vent means providing for communication with the interior of the upper portion of said chamber, said vent means including a vent passageway having an opening at one end thereof in communication with the interior of said auxiliary tank adjacent the upper portion of said chamber, said passageway having an opening at the other end thereof located at a point externally of said auxiliary tank; and said vent means further including a normally closed one-way check valve in sealing engagement with said vent passageway for normally preventing flow from said chamber through said vent passageway, said check valve permitting flow into the upper portion of said chamber whenever the pressure at said external point is greater than the pressure in the upper portion of said chamber to facilitate flow of fuel by means of gravity from said auxiliary tank through said discharge conduit to said carburetor whenever the float valve moves to the open position and the fuel pump is inoperative.
 2. A device according to claim 1, wherein said vent means includes a vent conduit providing communication between the interior of said auxiliary tank and a point located externally of said tank, the inner end of said conduit being positioned within the interior of said tank and having a valve seat formed thereon, said check valve including a movable ball valve member positionable in sealing engagement with said seat for preventing flow from the interior of said auxiliary tank to a point located externally thereof. 